Field of the Invention
The present invention relates to a process for recovering nickel from a byproduct of an electrolytic nickel manufacturing process by chlorine-leaching. The present application claims priority based on Japanese Patent Application No. 2014-164790 filed in Japan on Aug. 13, 2014.
Description of Related Art
In a conventional hydrometallurgical process of non-ferrous metal, with nickel sulfide as a raw material, which is a mixture of nickel, cobalt and else, produced by sulfuric acid leaching from low-grade laterite ore and nickel matte produced from pyrometallurgy, most of metals such as nickel, cobalt, copper and else contained in the raw material are chlorine-leached. And, in the hydrometallurgical process, an electrolytic nickel is manufactured by electrowinning after removing metal impurities and else from a solution obtained by chlorine-leaching.
Concretely, there is an electrolytic nickel manufacturing process (MCLE process) by chlorine-leaching, and its flow chart is illustrated in FIG. 7. As illustrated in FIG. 7, the electrolytic nickel manufacturing process comprises: a chlorine-leaching step S11 for generating a copper-containing nickel chloride solution, which is a chlorine leachate, by chlorine-leaching metal such as nickel with nickel sulfide as a raw material; a cementation step S21 for fixing univalent copper ion by adding nickel matte and chlorine-leached residue to the copper-containing nickel chloride solution obtained by the chlorine-leaching step S11; a solution purification step S31 for removing impurities other than nickel from a cementation final solution; an electrolytic step S41 for obtaining electrolytic nickel by electrominning from a nickel chloride solution obtained by the solution purification step S31; and a sulfur recovery step S51 for recovering product sulfur from the chlorine-leached residue obtained by the chlorine-leaching step S11.
In the electrolytic nickel manufacturing process, producing the copper-containing nickel chloride solution via chlorine-leaching with nickel sulfide as the raw material, manufacturing the electrolytic nickel from the copper-containing nickel chloride solution, and performing the cementation treatment for fixing and removing copper in the copper-containing nickel chloride solution efficiently, are important for manufacturing high quality electrolytic nickel. As the technology relating to this cementation treatment, for example, it is proposed in patent document 1.
However, in the electrolytic nickel manufacturing process, as illustrated in FIG. 7, copper contained in nickel sulfide will be fixed and removed from the chlorine leachate (copper-containing nickel chloride solution) obtained via the chlorine-leaching step S11 by transporting it to the cementation step S21. A cementation residue containing fixed copper will be returned to the chlorine-leaching step S11 again, and in the chlorine-leaching step S11, univalent copper ion becomes bivalent copper ion by reacting with chlorine gas, and nickel will be leached by oxidation power of the bivalent copper ion. In addition, copper contained in nickel matte is also fixed and removed as well as copper contained in nickel sulfide.
In other words, in the chlorine-leaching step S11 and the cementation step S21, copper is circulating in a state maintaining a prescribed concentration (normally 40 g/L to 60 g/L). Therefore, for example, when treatment capacity of nickel sulfide produced from hydrometallurgy is increased for the purpose of increasing manufacturing of electrolytic nickel, amount of copper circulated in a system of the electrolytic nickel manufacturing process will be increased inevitably.
By the way, in the cementation step S21, as mentioned above, the bivalent copper ion contained in the copper-containing nickel chloride solution will be reduced to univalent copper ion by nickel matte added as the raw material, and fixed by sulfur in the chlorine-leached residue.
However, nickel metal or nickel subsulfide, which is a major form of nickel matte, prioritizes a function to reduce bivalent copper ion to univalent copper ion, and univalent copper ion generated by remained nickel metal and else will be fixed as copper sulfide. Therefore, when the amount of copper circulating in the system of the electrolytic nickel manufacturing process is increased, relatively, amount of nickel matte for fixing as sulfide after reducing to univalent copper ion from bivalent copper ion will be decreased, so there is a case that copper in the copper-containing nickel chloride solution cannot be fixed and removed surely and efficiently.
Furthermore, when the amount of copper circulating in the system is increased by increased treatment of nickel sulfide as the raw material, along with increased manufacturing of electrolytic nickel, capability for removing copper will be insufficient with amount of nickel matte as well as conventional amount, in order to remove copper in the copper-containing nickel chloride solution, therefore the amount of nickel matte must be also increased, so it will not be possible to remove copper efficiently and effectively.
From the above reasons, in patent document 1, it is not possible to respond to the increase of the amount of copper circulating in the system, so the cementation treatment capable of removing copper contained in the copper-containing nickel chloride solution efficiently and effectively is desired.
In order to respond to this kind of demand, a technology for removing copper efficiently and effectively by fixing copper by adding nickel matte and chlorine-leached residue after reducing copper by adding nickel sulfide to nickel chloride solution containing copper (copper-containing nickel chloride solution) is proposed in patent document 2, patent document 3, and else. The technology described in patent document 2 and patent document 3 have been applied in real operation, and as a result, most of the above problems have been resolved.    Patent Document 1: Japanese Patent Application Laid-Open No. H11-080986    Patent Document 2: Japanese Patent Application Laid-Open No. 2012-107264    Patent Document 3: Japanese Patent Application Laid-Open No. 2012-026027